Last summer, Bera voted to delay the mandate for employers to provide insurance, but not for individuals to get insurance. Wednesday, though, he voted for a House Bill to delay the individual mandate, a key component of President Barack Obama's signature health care law.

In a press release, former California Rep. Doug Ose, one of three Republican challengers vying to oust Bera, paraphrased a line that famously sank Secretary of State John Kerry in the 2004 presidential race.

"Congressman Bera was for Obamacare's individual mandate before he was against it," Ose said. "He can't be 'kind-of' for Obamacare one day, and 'kind-of' against it the next."

Ose even took a shot at Bera's involvement in a bipartisan group called the No Labels Coalition. Wednesday's vote, Ose said, demonstrated that Bera couldn't make up his mind.

"Bera's 'No Labels Coalition' should be renamed the 'No Position Coalition,'" Ose said.

In a statement on his website, Bera characterized his vote as a response to the botched rollout of the Affordable Care Act last fall and a way to give people more time to sign up.

"While getting the uninsured coverage remains critical, there have been a whole host of problems with implementation starting with the roll-out of the website," Bera said, "and I couldn't in good conscience vote to penalize people who haven't yet enrolled."